Laminated foam mattresses which are designed to relieve or reduce the pressure exerted on the body of a person lying on the mattress are relatively conventional. As an example of the latter, U.S. Pat. No. 5,022,111 issued to William G. Fenner, Sr. on Jun. 11, 1991 discloses a triple layer laminated mattress having a middle layer formed of a first type of polyurethane foam and an upper and lower layer formed of a second type of polyurethane foam. The three layers forming the laminated mattress are said to work in conjunction to provide enhanced comfort and a reduction or relief in pressure on the user. The upper and lower layers also differ in density from the middle layer and include Indentation Load Deflection (ILD) values which are lower than the Indentation Load Deflection values of the middle layer.
Another typical multi-ply mattress is disclosed in Re. 32, 734 issued to Arlis D. McLeod on Aug. 23, 1988. The mattress thereof includes a firm mattress section separated from a soft mattress section by a stiffener board laminated therebetween.
Another mattress possessing particular utility in hospitals and nursing homes to reduce the incidents and severity of bed sores while improving muscle tone and reducing back ache is disclosed in U.S. Pat. No. 3,846,857 granted on Nov. 12, 1974 in the name of Clifford Weinstock. The mattress features a plurality of sections of foam whose densities and degrees of compressibility vary, so that regulated pressures will be applied to different sections of the body for maximum comfort. The mattress may be turned to change the pressure points of the body periodically, as need arises. An upper layer of the mattress is formed of several separate sections or slabs. A so-called head slab is recessed and accommodates therein an upper slab with these two slabs varying in density.
U.S. Pat. No. 5,745,940 issued on May 5, 1998 to Derek Roberts et al. discloses a mattress which is made from four so-called comfort modules having different indentation force deflection (IFD) values which are secured to each other. Such modules are interchangeable and can be stacked in a comfort module chamber to essentially construct a mattress to accommodate the specific weight of a person.
U.S. Pat. No. 5,430,901 issued on Jul. 11, 1995 to David L. Farley discloses in FIG. 12 nine different pieces of material assembled together to form a single mattress to set-off regions of comparatively differing firmness/softness.
Another mattress constructed essentially as a polyurethane foam base with a polygonal recess into which is inserted an insert is disclosed in U.S. Pat. No. 5,107,558 issued on Apr. 28, 1992 to Werner Luck. The insert may vary in its construction and three specific examples are given, including in each case an envelope filled with (a) fragments of polyurethane foam, (b) two layers of polyurethane foam and (c) a mixture of polyurethane rods and beads. All of this is provided to assure differing degrees of firmness/softness.
In U.S. Pat. No. 5,031,261 granted on Jul. 16, 1991 to William G. Fenner, Sr., a laminated foam mattress is disclosed which is formed of two layers bonded to each other. A base layer is constructed from polyurethane foam material of a specific density differing from an upper layer, likewise being formed from polyurethane foam. The two layers differ in Indentation Load Deflection values.
In U.S. Pat. No. 4,673,452 granted on Jun. 16, 1987 to Deo P. Awdhan, several different mattresses are disclosed including a two-ply mattress, a three-ply mattress and a three-ply mattress bounded by a peripheral frame with at least one of the plies or layers being convoluted.
In U.S. Pat. No. 4,768,251 granted on Sep. 6, 1988 to Feyyaz O. Baskent, a mattress pad is disclosed which includes a center section into which is inserted a pair of superimposed laminates or plies constituting a torso support insert member made of polyurethane material.
The latter prior art patents include many disadvantages, including all of those referenced in U.S. Pat. No. 5,022,111, namely, insufficient pressure reduction, poor body-to-mattress conformance, discomfort due to rigid foam or discomfort due to bottoming out of soft foam or foam inserts, etc. Moreover, manufacturing costs for such prior art mattresses are relatively exorbitant, again as is referenced in U.S. Pat. No. 5,022,111.